It's kind of correlated with size - the smaller the animal is, the easier it is to survive after losing a limb. For a horse, even a broken leg is likely to be fatal.

A missing foot is survivable for a lynx much more so than for a human in the absence of modern medical care.

The same applies for evolutionary pressure in the case of hypothetical regeneration. A lizard can take ~2 months to regenerate a limb, for a human it would take longer simply since the limb is larger and needs to grow more. Prehistoric humans and hominids were calorie limited - if an injured individual is capable and likely to (a) survive for e.g. half a year with the injury and (b) to obtain much more calories than normal to rebuild many pounds of tissue, then apparently there is no strong evolutionary pressure to favor regeneration it as he/she is capable of procreating almost as well even without this feature.